通过IoC向工厂类提供依赖关系？ [英] feeding dependencies to a factory class via IoC?

问题描述

我有一个工厂类，决定应该实例化和返回四个可用的子类中的哪一个。正如你所期望的，所有的子类实现相同的接口：

I have a factory class that decides which of four available subclasses it should instantiate and return. As you would expect, all subclasses implement the same interface:

public static class FooFactory{
     public IFoo CreateFoo(FooEnum enum){
            switch (enum)
            {
                case Foo1:
                    return new Foo1();
                case Foo2:
                    return new Foo2();
                 case Foo3:
                    return new Foo3(IBar);//has a constructor dependency on IBar
                case Foo4:
                    return new Foo4();
                 default:
                    throw new Exception("invalid foo!");
            }
     }
}

的子类具有在其构造函数中定义的依赖关系。

As you can see, one of the subclasses has a dependency defined in its constructor.

有些兴趣点：

• 我们使用Spring.NET我们的Io​​C。


• IFoo 的所有子类都是域对象，因此不会被Spring.NET实例化。


• 应用程序有一个手写的数据访问层（puke），所以没有ORM在这里播放。

• We're using Spring.NET as our IoC.
• All subclasses of IFoo are domain objects and therefore are not being instantiated by Spring.NET. I'd like to keep things this way if at all possible.
• The application has a hand written Data Access Layer (puke) so no ORM is in play here.

我想知道如何最好地将 IBar 依赖项传递到 Foo3 从 FooFactory 。我得到的感觉，这可能是一个问题最好通过IoC解决，但我不能grok如何。我也想保持 FooFactory 尽可能单元测试：ie我不想在我的测试代码中依赖于Spring.NET。

I'm trying to figure out how best to pass the IBar dependency into Foo3 from FooFactory. I get the feeling that this might be a problem best resolved via IoC but I can't quite grok how. I also want to keep FooFactory as unit testable as possible: i.e. I'd prefer not have to have dependencies on Spring.NET in my test code.

感谢阅读。

推荐答案

将FooFactory更改为 >并注入IBar实例到具体的实现，像这样：

Change FooFactory to an Abstract Factory and inject the IBar instance into the concrete implementation, like this:

public class FooFactory : IFooFactory {
     private readonly IBar bar;

     public FooFactory(IBar bar)
     {
         if (bar == null)
         {
             throw new ArgumentNullException("bar");
         }

         this.bar = bar;
     }

     public IFoo CreateFoo(FooEnum enum){
            switch (enum)
            {
                case Foo1:
                    return new Foo1();
                case Foo2:
                    return new Foo2();
                 case Foo3:
                    return new Foo3(this.bar);
                case Foo4:
                    return new Foo4();
                 default:
                    throw new Exception("invalid foo!");
            }
     }
}

注意FooFactory现在是具体的非静态类实现IFooFactory接口：

Notice that FooFactory is now a concrete, non-static class implementing the IFooFactory interface:

public interface IFooFactory
{
    IFoo CreateFoo(FooEnum emum);
}

在您需要IFoo实例的代码中，依赖于IFooFactory并使用它的CreateFoo方法来创建你需要的实例。

Everywhere in your code where you need an IFoo instance, you will then take a dependency on IFooFactory and use its CreateFoo method to create the instance you need.

你可以使用任何一个值得使用的DI容器来连接FooFactory及其依赖。

You can wire up FooFactory and its dependencies using any DI Container worth its salt.

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